Fibromyalgia (FMS) is a common, chronic musculoskeletal disorder and a growing cause of disability and medical care costs. With a poorly understood etiology and no known cure, current pharmacological treatment is mostly ineffective. Cardiovascular and flexibility forms of exercise have been reported to be beneficial and are often recommended However, there is a high rate of injury from exercise in the FMS population, and consequently, a very poor compliance rate with long-term exercise. Therefore, the long-term objective of this project is to optimize the exercise recommendations for persons with FMS and to identify factors to facilitate long-term compliance. The study aims to determine the efficacy of adding strength training to current exercise recommendations and to identify variables that potentially predict long-term exercise compliance in persons with FMS. This proposed project is a randomized controlled, intervention study comparing a program of strength training, cardiovascular and flexibility exercise (experimental) to a program of cardiovascular and flexibility exercise (current recommendation). Each program will include three group exercise sessions per week for 20 weeks. Upon completion of the group intervention, all subject will be given a copy of their exercise program, a diary/calendar for recording their exercise activities and will be followed for 6 months to examine exercise adherence and long-term effects. Subjects will be 150 women, 25 to 60 year old with a diagnosis of FMS, plus any men wishing to participate. Recruitment will be accomplished through direct referral from primary care physicians and rheumatologists, and through newspaper advertisements. Testing will occur a baseline, completion of the 20-week intervention and at 3 and 6 month follow up. Testing will assess health and functional status (FIQ SF36), symptom severity (FIQ SF36, Beck Depression Inventory), muscle strength (IRM) cardiovascular fitness (modified Bruce protocol), flexibility (Sit-and-Reach), and self-efficacy (Arthritis Self-Efficacy Scale). The expected outcomes of this study will advance the treatment paradigm for FMS by establishing an evidence based exercise prescription that can be integrated into a standard treatment plan and by identifying modifiable variable that may be used to facilitate long-term exercise maintenance in this population.